Identification of prokineticin-2 as potential pharmacodynamic biomarker for overcoming doxorubicin resistance in multicellular breast cancer spheroids.

[BACKGROUND AND PURPOSE] Despite advances in immunotherapy, doxorubicin (Dox) chemotherapy is still the irreplaceable first-line therapy for solid tumours such as breast cancer. However, chemotherapy resistance is the major limiting factor, requiring the use of high doses of Dox to achieve the anti-tumour actions, often leading to severe side effects. Unravelling the mechanisms behind chemoresistance and identifying potential biomarkers for mitigating this resistance could enhance current treatment strategies and improve patient outcomes.

[EXPERIMENTAL APPROACH] We developed human 3D breast cancer spheroids (HBCSs) as a model that closely mimics in vivo tumour structure and microenvironment. Given that hypoxia and elevated levels of the angiogenic cytokine, prokineticin-2 (PK2), are associated with chemoresistance to antiangiogenic therapy, we explored the effect of a hypoxia-inducible factor (HIF-1α) inhibitor on viability defect in HBCSs and the levels of PK2 in the conditioned medium following Dox treatment. We also assessed levels of HIF-1α, active caspase-3, TUNEL and reactive oxygen species (ROS), and CD73 enzymatic activity in HBCSs.

[KEY RESULTS] Results showed that HIF-1α inhibitor increased viability defect in the Dox-resistant HBCSs. Interestingly, at higher Dox concentrations, chemoresistance was mitigated independently of HIF-1α and promoted apoptosis and ROS accumulation, which were correlated with PK2 release.

[CONCLUSIONS AND IMPLICATIONS] Our findings provide the first evidence that PK2 may serve as a predictive pharmacodynamic marker, offering a potential strategy to overcome drug resistance in targeted cancer therapy.